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authorMinchan Kim <minchan@kernel.org>2017-01-10 16:57:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-10 18:31:55 -0800
commit20f664aabeb88d582b623a625f83b0454fa34f07 (patch)
tree5e4c10fdaab60ea66e69d7c92f1b06b0565573f2
parentc626bc46edb0fec289adfc86b02e07d34127ef6c (diff)
downloadlinux-20f664aabeb88d582b623a625f83b0454fa34f07.tar.bz2
mm: pmd dirty emulation in page fault handler
Andreas reported [1] made a test in jemalloc hang in THP mode in arm64: http://lkml.kernel.org/r/mvmmvfy37g1.fsf@hawking.suse.de The problem is currently page fault handler doesn't supports dirty bit emulation of pmd for non-HW dirty-bit architecture so that application stucks until VM marked the pmd dirty. How the emulation work depends on the architecture. In case of arm64, when it set up pte firstly, it sets pte PTE_RDONLY to get a chance to mark the pte dirty via triggering page fault when store access happens. Once the page fault occurs, VM marks the pmd dirty and arch code for setting pmd will clear PTE_RDONLY for application to proceed. IOW, if VM doesn't mark the pmd dirty, application hangs forever by repeated fault(i.e., store op but the pmd is PTE_RDONLY). This patch enables pmd dirty-bit emulation for those architectures. [1] b8d3c4c3009d, mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") Link: http://lkml.kernel.org/r/1482506098-6149-1-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reported-by: Andreas Schwab <schwab@suse.de> Tested-by: Andreas Schwab <schwab@suse.de> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Jason Evans <je@fb.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: <stable@vger.kernel.org> [4.5+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/huge_memory.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 72339a646fb1..9a6bd6c8d55a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -883,15 +883,17 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
{
pmd_t entry;
unsigned long haddr;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
goto unlock;
entry = pmd_mkyoung(orig_pmd);
+ if (write)
+ entry = pmd_mkdirty(entry);
haddr = vmf->address & HPAGE_PMD_MASK;
- if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry,
- vmf->flags & FAULT_FLAG_WRITE))
+ if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
unlock: